Understanding Non-Completion of the Human Papillomavirus Vaccine Series: Parent-Reported Reasons for Why Adolescents Might Not Receive Additional Doses, United States, 2012

Abstract

Completion rates of the human papillomavirus (HPV) vaccine series among U.S. adolescents are below public health targets. We explored parent-reported reasons for their children's non-completion of the HPV vaccine series using a nationally representative online survey of parents of children aged 9–17 years, fielded in October 2012. Among the 1,653 parents who responded, the proportion reporting that their child would definitely continue with the HPV vaccine series among those who had started the series ranged from 28% to 54%. The most common reason cited by parents for non-completion of the series was their child's fear of needles, followed by lack of awareness about additional doses and safety concerns. These findings demonstrate the need to encourage adoption of strategies addressing needle fears, utilize reminders for parents about subsequent doses, and emphasize recent HPV vaccine safety data in discussions with parents.

Routine vaccination with human papillomavirus (HPV) vaccine is recommended for U.S. adolescents at ages 11–12 years.^1,2 The currently recommended schedule is a three-dose series, with follow-up dosing two and six months after the initial dose.³ National data from 2013 for adolescents aged 13–17 years show low rates of receipt of all three HPV vaccine doses (38% of girls, 14% of boys) and low rates of HPV vaccine series completion among those who had received at least one dose (70% of girls, 48% of boys).⁴

Understanding the reasons for non-completion of the HPV vaccine series may help inform strategies to increase completion rates. Past studies of adolescent girls show an association between HPV vaccine series completion and certain patient demographics. For example, HPV vaccine series completion rates have been low among non-Hispanic black girls and those without health insurance.^5,6 Several studies have linked lower rates of HPV vaccine series completion to lack of awareness of the need for additional doses^5,7 or lack of a recommendation from or discussion with a health-care provider.^5–8 No published studies have focused on parental perspectives on series completion for their adolescent children who started the HPV vaccine series. We explored parental reasons for non-completion of the HPV vaccine series by their adolescent children who received the initial dose.

METHODS

We conducted a cross-sectional survey of parents of children aged 9–17 years in the United States using KnowledgePanel^® (GfK Custom Research North America, New York, New York), a nationally representative panel used for online surveys. KnowledgePanel members are selected using address-based probability sampling, representing approximately 97% of U.S. households.⁹ Households are provided with Internet access and hardware, if needed.

The 22-question survey, available in English and Spanish, included questions on HPV vaccine receipt and future intention, reasons for nonreceipt, and physician recommendations. Questions were pretested with a sample of 100 KnowledgePanel members. KnowledgePanel has been used for prior HPV-related studies,¹⁰ and survey questions were adapted from prior vaccine-focused studies using KnowledgePanel.^11–13 Reasons for non-completion of the HPV vaccine series were drawn from studies of parental concerns about HPV vaccine.^5,7,8

Survey invitations were e-mailed to 3,177 KnowledgePanel members identified in GfK profile data as being parents of ≥1 child aged 9–17 years. A total of 1,799 (57%) KnowledgePanel members completed the online survey from October 17 to October 31, 2012, and 1,653 of the 1,799 survey respondents reported being the parent of ≥1 child aged 9–17 years (92% eligibility).

Respondents reported the age, sex, and number of HPV vaccine doses received (none, one, two, or three doses) for each of their children aged 9–17 years. For each child who had received one or two doses, respondents were asked whether that child would receive additional doses within the next 12 months (definitely, probably, probably not, or definitely not). When respondents answered probably, probably not, or definitely not, they were asked to indicate (with yes/no responses) reasons why not.

GfK provided de-identified data and used U.S. Census-based post-stratification weights to match the U.S. population distribution on parent sex, age, race/ethnicity, education, and U.S. Census region. We generated frequency distributions and bivariate analyses using SAS^® version 9.3.¹⁴ We used bivariate analyses to explore the reasons for nonreceipt of additional HPV doses in the next 12 months by child sex, by sex and age group (9–12 vs. 13–17 years), and by intention (probably vs. probably not or definitely not receive additional doses). We calculated unweighted frequencies and weighted proportions.

RESULTS

All 1,653 respondents completed data on age, sex, and number of HPV vaccine doses received for 2,511 children aged 9–17 years. Receipt of three HPV vaccine doses (i.e., the number of doses in a full series) was more common among adolescent girls aged 13–17 years (n=210, 27.3%) than among boys in either age group or girls aged 9–12 years (n=35, 5.8%). Among the 438 children aged 9–17 years who had received one or two doses of HPV vaccine, the proportion who would definitely receive additional doses in the next 12 months was highest for girls aged 9–12 years (n=48, 54.0%) and lowest for boys aged 9–12 years (n=26, 28.2%). Only 10 parents reported that their child would definitely not receive additional doses (Table 1). Eighty-three respondents reported having more than one child who had received one or two doses.

Table 1.

Parental report of human papillomavirus (HPV) vaccine receipt among children aged 9–17 years and parental intent for their child to receive additional doses among those with one or two doses, United States, October 2012^a

^aData collected via a KnowledgePanel^® online survey of parents of adolescents aged 9–17 years (n=1,653 eligible respondents, representing 2,511 children aged 9–17 years). Results shown as unweighted frequencies and weighted proportions.

^bThese data were missing for four children.

CI = confidence interval

For the 250 adolescents who would probably, probably not, or definitely not receive additional doses of HPV vaccine in the next 12 months, the most common reason cited by parents was “my child does not like needles” (n=90). Multiple reasons for non-completion were reported for 102 adolescents (mean = 1.8 reasons, median = 1.0 reason across all 250 adolescents). Among respondents who chose more than one reason, the combination of reasons most commonly cited related to lack of awareness about additional doses (i.e., “my child's doctor did not tell me more shots were needed” and “I do not think my child needs additional shots of HPV vaccine”). This combination of reasons was indicated by 49 parents of girls and 61 parents of boys. Fifty-seven parents indicated that hearing about problems with HPV vaccine was a deterrent to non-completion for their child, although only 12 parents said their child had had a problem with an HPV dose. Fifty-two parents did not cite any reason, and nearly all of them said their child would probably receive additional doses (Table 2).

Table 2.

Parent-reported reasons for child not receiving additional human papillomavirus (HPV) vaccine doses in next 12 months among children aged 9–17 years with one or two HPV doses, United States, October 2012^a

^aData collected via a KnowledgePanel^® online survey of parents of adolescents aged 9–17 years (n=1,653 eligible respondents, representing 2,511 children aged 9–17 years). Results shown are unweighted frequencies and weighted proportions. Denominator used in calculating percentages is number of adolescents with one or two HPV vaccine doses whose intent to receive additional doses in next 12 months was probably, probably not, or definitely not. Column percentages do not total to 100 because respondents could choose more than one reason.

CI = confidence interval

Parents of boys aged 9–12 years more often cited the reasons “my child does not like needles” (70.1%, 95% CI 54.9, 85.2) and “I do not think my child needs additional shots of HPV vaccine” (52.6%, 95% CI 34.3, 70.9) than did parents of boys aged 13–17 years (35.1%, 95% CI 18.9, 51.2, p=0.004 for “my child does not like needles” and 23.0%, 95% CI 9.9, 36.0, p=0.006 for “I do not think my child needs additional shots of HPV vaccine”). We found no other age-based differences for boys or girls in reasons for not receiving additional HPV vaccine doses. We also found no differences in reasons for not receiving additional HPV doses between boys and girls.

In sex-stratified analyses comparing those who would probably vs. probably not or definitely not receive additional doses, we found no significant differences among parents of boys in reasons for not receiving additional doses. Among parents of girls, parents who said their daughter would probably receive additional HPV vaccine doses were significantly more likely to indicate “it is inconvenient to come back to the doctor's office for additional doses” as a reason that their child might not receive additional doses (31.5%, 95% CI 18.1, 44.9) compared with parents who said their daughter would probably not or definitely not receive additional HPV vaccine doses (11.0%, 95% CI 0.3, 21.8, p=0.03).

DISCUSSION

With regard to the gap between HPV vaccine series initiation and completion, this study underscores parent-reported children's dislike of vaccination as a key contributor to intended non-completion of the HPV vaccine series. Fear of needles, rooted mainly in the anticipation of and past experiences with injection pain, was prevalent.¹⁵ Although evidence-based strategies and clinical practice guidelines to manage needle pain are well documented,^16–20 practice-level adoption of these strategies is low.^15,21,22 Adolescent vaccination poses a unique decision-making dynamic,^23–25 because adolescents are more likely than younger children to be involved in their parents' decisions about their health care. Studies show that adolescent attitudes (e.g., fear of needles) can discourage parents from accepting vaccines,^23,25 especially vaccines such as the HPV vaccine that are not typically required for school. A recent study showed that parental reports of their children's fear of needles underestimate the extent of needle fear reported by their children.²⁶ In addition to adopting interventions addressing fear of needles, it will be important for providers to explain to adolescents and their parents why the needle sticks are worthwhile for protection against HPV.

Another key contributor to non-completion is parents' lack of awareness of the need for additional doses. This lack of awareness represents an opportunity for both public health officials, who can emphasize the three-dose recommendation in media campaigns and implement reminder/recall notifications that promote the importance of series completion, and practitioners, who can focus on series completion in their discussions with families and conduct practice-based reminder/recall. However, further research is needed to explore whether parents' perceptions of need may be related to their knowledge and beliefs about the timing of vaccination (e.g., the question of whether HPV vaccine is only effective if given prior to initiation of sexual activity) or the effectiveness of two-dose HPV regimens (e.g., recommendations in other countries).

Many respondents indicated they had heard of problems with HPV vaccine; this idea could be countered through public health messages that include information about HPV vaccine safety. Convenience and cost, although not the primary barriers to non-completion, may impede series completion when no other barriers exist.

Limitations

This study was subject to several limitations. First, our ability to examine subgroup differences was limited by the small sample sizes. Second, one-quarter of respondents described reasons for non-completion for more than one child; although reasons may differ between boys and girls and between older children and younger children, parental views may be correlated across multiple children. Third, although KnowledgePanel provides Internet access to recruited households as needed, it is possible that this strategy does not fully ameliorate the underrepresentation of families without home Internet access. Fourth, the study was limited by a lack of clinical verification of HPV vaccine receipt; however, parental report has been shown to be a -reasonable -approximation of provider-reported rates.²⁷ Fifth, the rates for completion of ≥1 dose of HPV vaccine from this study were slightly lower for girls and higher for boys compared with national, provider-verified rates among adolescents aged 13–17 years in 2012, which may have been because of the substantially lower participation rates for the national provider-verified data.²⁸ Finally, HPV vaccination rates have increased since the time that study data were collected, and reasons for non-completion may have shifted.

CONCLUSION

The majority of parents reported at least some level of intent for their adolescent child to continue with the HPV vaccine series among those who started the series. To help ensure follow-through on this intent, immunization providers and public health officials should adopt strategies that address parental reasons for series non-completion, such as adolescents' fear of needles, parents' lack of awareness about the need for additional vaccine doses, and vaccine safety concerns.